Color television reproducing systems



Apri! 17, 1956 G. c. szlKLAl COLOR TELEVISON REPRODUCING SYSTEMS 2 Sheets-Sheet l Original Filed Sept. 24-,l 1949 INVENTOR wwm mwq SSG, ber

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COLOR TELEVISON REPRODUCING SYSTEMS Original Filed Sept. 24, 1949 2 Sheets-Sheet 2 Geo e Lzildai 1"' United States Patent O l2,742,524 v f COLOR TELEVISION REPRDUCINGr SYSTEMS George C. Sziklai, Princeton, N. J., assignor to Radio l Corporation of America, a corporation of Delaware Continuation of application Serial No. 117,533, September 24, 1949. This application December 12, 1951, Serial No. 261,187

26 Claims. (Cl. 17g-5.4)

This invention relates to vcolor television systems and particularly to systems and apparatus for reproducing images substantially in their natural colors.

This application isa continuation of my application, Serial No. 117,533, liled September 24, 1949, now abandoned, and entitled Color Television Reproducing Systems.

There previously have been proposed numerous sys-v tems for the pickup, transmission and reception of video signals representative of selected primary color components of an'image for the reproduction at a signal-receivi ing point of the original images substantially in their natural colors.- In view of the fact that there presently is a large number of monochrome television receivers in daily operation, it is highly desirable that any ,color television system which is adopted be of such a character that it will not render obsolete any of the present monochrome receivers. Furthermore, it also is desirable that thecolor television system which is adopted to be of such a character that the modification of the existing mono- Y chrome receivers for the reproduction ofcolored imagesbe made as simple as possible. In addition, in order yto' minimize the cost of a color television reproducing apparatus, it is necessary to add as few as possible components to the receiver and yet have the' receiver capable of reproducing colored television images having a relatively high entertainment value.

One of the proposed color television systems operates colors by utilizing only three component primary colors.

However, an image reproducing apparatus, which lis. to be responsive to video `signals of the characterdescribed, requires considerable apparatus in addition to tht'needed for monochrome image reproduction.y For example, -in one type of image reproducer, `a separate, kinescope and its necessary auxiliaryapparatuspis required for each `of the component primary colors which, i

in the case where three such colors are utilized, necessitates the employment of three kinescopes.

It has further been determined that reasonably good:

images may be reproduced in a smaller number of colors than those represented by the transmitted signals. Ina

three-color television system, for` example, images may be reproduced in suiciently close approximations of their original colors to provide considerable .entertainment value by suitably combining dilerent pairs of the of this condition, some of the receiver kinescopes which. otherwise would ber needed may be eliminated so that `inv,

It has been determinedtthat images may be reproduced in substantially theirnatural v three component primary colors.y By taking advantage i a three-color system, for example, only two kinescopes are necessary. Also, in an arrangement of this character,` a much simpler optical system may be employed to com-.1

bine in registry the partial color images of the two kinescopes than in the case where the combination of the partial color images produced by three or more kinescopes is required.

A further advantage may be derived, bythe utilization of this knowledge of the capabilities of a system operating according to the dot multiplex principle, in the design of a relatively simple and inexpensivepadaptor for usein conjunction with an existing monochrome receiver for the purpose of enabling it to.V reproduce images in substantially their natural colors. y

An object of the present invention is to provide for ob-r taining, from a complex color signal obtained by sampling video signals representing dilerent component colors at predetermined time intervals, asgnal output representingy the predetermined time intervals.

According to this invention, there may be advantageous-` ly provided an improved color television'receiving system by which video signals vgenerated and transmitted acsamples of the complex color signal taken at other than cording to the dot multiplex or signal sampling principle may be satisfactorily reproduced in asmaller number off component colors than the-total number yof component colors represented by the received signals.

According to this invention in any aspectv thereof, diff, ferent pairs of the received color video signals are com-v bined in such a manner as to produce single colors each of which, in effect, is a pre-selected mixture of the two colors represented by each of the pairs of signals. v Such a'r'esult is produced according to this invention by suitably timing the impression of the received signals upon'they image reproducing kinescopes to coincide with a selected interval occuring between the time of reception ofthe two color signals selected. vThe timing is effected by suitably phasing, with respect to the received signal wave, the operation of a plurality of keying yor sampling devices interposed between the signal receiving circuits and -the respective kinescopes.

Another object ofthe invention, therefore is to pro-; vide a relatively simple and effective color television 'receiving system, whereby the image may be reproduced` in a smaller number of color components than are presentl in the received signals.

A further object of the invention is to provide an improved color television vreceiving system, whereby there may be utilized phases of thereceived three-color repre-l sentative video signal wave whichare different from those' representing the original component image colors.

Still another object ol"v this invention is to provide .an improved color television receiving system, whereby an existing monochrome receiver may bek easily adapted for the reception and reproduction of color television signals;

Other and incidental objects of the invention will be' apparent to those skilled in theart from a reading of the following specification and an inspection of the accompanying drawings in which:

Figure l is a vcircuit diagram, partly in block form,y

of an illustrative embodiment ofthe invention; and

Figure 2 is a graphical representation of the manner in i which the apparatus of Figure l operates according to the invention.

Referring now particularly to Figure l of the drawings,

there is illustrated alconventional television carrier wave receiver and signal detector 11 which it will be underr stood may include ,one or more stages-of radio frequency amplification, a frequency converting Vst agefone -or more stages ot" intermediate frequency amplification, and a Patented Apr. 17, k1.956

secondr or signal detector by means of which the modulationl envelope of the received carrier is recovered. The modulation envelope includesa portion which corresponds toa composite color video signal Wave. The outputV of the receiver and' detector apparatus 11 is coupled to an amplifier 1 2- which functions to amplify the composite television signal including the video and` system control' signals such as the synchronizing pulses. In -the following description of an illustrativeembodimentl ofA the invention, it will be assumed that the received composite video-signal wave comprises three individual color video signals representing respectively the green, red and blue color components of the original image; and the image which is t be reproduced will have orange` (combination of. greenand red) and cyan (combination of blue and green) color components. The output ofthe amplifier 12-is coupled to the input circuits a pair of gating or keying devices 13 and 14 which normally are biased to a non-conducting, i. e. inoperative state. 1n such a state, the gating devices are inoperative to transfer signals from their input circuits to their associated output circuits. The output circuit of the keying device 13 is coupled to an orange video signal amplifier which functions-to amplify a selected combination of the green and'red color video signals. Similarly, the output circuit of the keying device 14 is coupled to a cyan video amplifier 16 which functions to amplify a selected combination of the blue and green received color video signals, The output circuits ofthe video signal amplifiers 15"and 16A are coupled respectively to the electron beam intensity control electrodes of an orange image kinescope 1 7-and a cyan image kinescope 18. Each of these kinescopes may be provided with suitable color phosphors or filters, or both, and the images reproduced thereby suitably combined by means of a light dividerl19 and a projection optical system 21 so as to reproduce the two partial color images exactly in register on a viewing screen 22.

The output circuit of the amplifier 12 also is coupled to a horizontal synchronizing pulse generator 23 by means oflwhich the synchronizing signals are conventionally separated from the video signals and impressed upon the deflection circuits for the image reproducing kinescopes as indicated. The output circuit of the horizontal synchronizing pulsegenerator 23 `is coupled to the control circuit of a pulsed oscillator 24; The oscillator 24 may have any desired form such as, for example, that shown in the text book entitled Wave Forms published in 1949 by the McGraw-Hill Book Company, Inc., at page 143, Figure 4-45. The details of such an oscillator also are shown in the copending application ofJohn Evans referred to Y previously. It only is essential that the oscillator be capable of stable oscillation at a frequency, corresponding to the frequency of each of the component color signals and be susceptible of control by means of the horizontal or line frequency synchronizing pulses. the pulsed oscillator 24, therefore, is a sinusoidal voltage having the frequency of any one of the received color The. output of television video signals which is impressed upon a phase shiftingdevice 25. The phase shifting device is provided with two output circuits in respective ones of which are developed voltage impulses at the frequency of the color television signals.

The output circuit voltages of the phase shifting device, however, are 120 electrical degrees out of phase, and. are respectively coupled to the keying devices 13 and 14 so that they are rendered operative respectively 120 degrees out of phase with one another. Furthermore,V the output circuit voltages of the phase shifting device are phased relative to the received composite three-color video signal wave so that the keying devices `are rendered operative at suitable intervals occurring between the reception of different pairs of color video signals to impress properly mixed signals upon the kinescopes 17 and 18, whereby to reproduce the desired color combinations.

The phase shifting device 25 comprises two electronic tubes 26 and 27 which for simplicity, are shown herein as triodcs. lt will be understood, however, that the invention is not necessarily limited to the use of tubes of this character but may instead embody other types of tubes such as pentodes, for example. The two tubes 26 and 27 are provided respectively with input and output circuits of a character to permit the development in the respective output circuits of voltages having the desired phase relationship to control the operation of the keying devices 13 and 14 in the manner described. Specifically, the output circuit of the pulsed oscillator 24 is coupled to the control grid of the tube 26 by a circuit which includes the series resistors 27 and 28 and a resistor 29 connected in shunt to ground. The output circuit of the oscillator 24 also is coupled to the control grid of the tube 27 by a circuit which includes the series arrangement of a capacitor 31 and a resistor 32 and also a resistor 33 connected in shunt therewith to ground. Preferably, the capacitor 31 is variable in order to suitably adjust the phaserelatlonship of the output voltage of the tube 27 with respect to that of the tube 26 and also with respect to the received color video signals. Each of the tubes is provided witha conventional self-biasing circuit arrangement which'for the tube 26 includes a resistor 34am! a by-pass capacitor 35 and for the tube 27 includes a resistor 36rand an associatedby-pass capacitor 37.

The output circuit of the tube 26 includes a phase shifting-network comprising a resistor 38 anda variable capacitor 39 connected in shunt-therewith. A primary coupling transformer winding 41 also is connected to the anode of the-tube 26 in parallel with the phase shifting network and space current for-the tube is provided from a suitable source of energy indicated at -l-B through a voltage-dropping resistor 42. Similarly, the output circuit of the tube 271includes a phase shifting network comprising a resistor 43 and a variable capacitor 44 connected in shunt therewith and alsoV a coupling transformer primary winding 45 connected in parallel with the phase shifting network. Space current for the tube 27 is provided by means of a connection to a source of unidirectional energy indicated at -l-B through a voltage-dropping resistor 46.

The primary winding 41 is inductively coupled as indicated;to a secondary winding 47 forming a part of the keying device 13. The secondary winding is coupled to conjugate terminals of a rectifier bridge network 48 by means including an energy storage network comprising a shunt arrangement of :a capacitor 49 and a resistor 51 in order to bias the bridge-network alternately for conduction and non-conduction for the desired selection of the received .video signals for impression upon the orange kinescope 17. The biasing terminals to which the secondary winding 47fis connectedmay be by-passed to ground, if desired, by means of capacitors 52 and 53 in order to neutralize any distributed capacitance of the winding 47 and associated circuit elements.

In likemanner, the primary winding 45 is inductively coupled to a secondary winding 54 included in the keying device 14 and this secondary winding is connected by means of a biasing network comprising a parallel connection of a capacitor 55 and a resistor 56 .to conjugate biasing terminals of a-rectifier bridge network 57, which terminals also may be `by-passed to ground by neutralizing capacitors 58 and 59.

The composite received color video signal waveis irnpressed upon each-of the networks 48 and 57 by means of a connection between the output circuit of the amplifier 12 and an input one of the other two conjugate terminals of the rectifier networks. The other, or output, terminals of the respective recter networks are connected to the respectiveoutput circuit impedance devices which for the keying device 13 includes resistors 61andf62` connected betweenV a suitable source. of unidirectional` positive voltage and ground and for4 the keying device 14 includes resistors 63 and 64 similarly connected.

4A yvariable rap 65 on nie'iresisto 6'1 is oupiea by' a" capacitor A66 tothe input circuit of the orange video signal j amplier 15. In like manner a variabletap 67 on the resistor 63 is coupled by a capacitor 68 to the-input cir" cuit of the cyan video signal lamplifier 16. By such means, the selected combinations of the receivedcolor video signals are utilized to energize the orange and cyan kinescopes 17 and 18, respectively.

- Before referring in detail to the manner in which the described apparatusoperates, to effect aL reproduction of a two-color image from a-three-color received signal,

reference will be made briefly to the manner in which the phase shifting device 25 maybe adjusted to effect the desired phase relationship between the/two output voltages thereof and also with respect to the received video signals. It is seen thatthesinusoidal output voltage derived from the pulsed oscillator 24 is impressed lupon the input circuit of the tube 26 substantially without any phase shifting.

However, by suitable adjustment of the-'variable capacitor 31, the phase of the voltage impressed upon the inputV the voltages developed in the respective primary windings 41 and 45 of such a character that the voltage in the winding 45 leads the voltage developed in the winding 41 by'approximately 60".y If now the primary windings 41and 45 are coupled to their respectivesecondaryV windings 47 and 54 in'opposite polarity, the voltage developed in winding 47 leads the voltage developed i'nthewinding 54 by approximately 120. Furthermore, it willbe understood that the capacitors 31, 39 and 44 are adjusted to produce the proper phase relationship vbetweenfthe voltages inthe secondary windings and the received color video signals to impress properly mixed signals upon the kinescopes 17 and 18 so that they will display the desired combination colors.

Normally, the rectifier bridge networks 48 and 57 comprising the gating devices are biased to a non-conducting state so that the video signal voltages impressed' upon the input terminals thereof do not eifect the development of corresponding voltages in the output circuit'thereof.

The impulsive voltages which are developed in the secondary windings 47 and 54 in the manner described condition the respective networks 48 and 57 for momentary conduction, whereby those portions 'of the received vcomposite color video signal wave which is impressed upon the input terminals of thenetworks are effective to develop corresponding mixed video signal voltages in the output circuits of the bridge networks for impression ultimately upon the respective kinescopes 17 and 18. 1

The manner in which the apparatus of Figure 1 operates to properly time the impression of the selected portions of the received composite color video signal wave upon the image reproducing kinescopes 17 -and 18, whereby to develop a two-color image from three-color signals will best be understood by having additional reference to the curves of Figure 2.. vIn Figure 2, the curve 69 represents the sinusoidal voltage wave derived from the output circuit of the pulsed oscillator 24 and having a frequency corresponding to the frequency of recurrence of any one of the three-color signal components. It will be understood that only the positive half cycles of this wave, or ifdesired only the crests of these positive half cycles, are effective to control the operation of the rectifier networks 48 and 57. It will'be assumed for explanatory purposes that the crests of the wave 69 occur in substantial coincidence with the reception Vof those. portions ofthe receivedVr composite color' video signal wave which represent a particular color'of the yimage to be reproduced.l 9 For example, in this case, vit will'be assumed that jthevcr'ests of the wave 69 occur in coincidence with the reception of the red video signal components.- It will be understood, however, f that the crests of the wave 679 may occur coincidentally` with any of the other color representative video signal components. d

The curve 70 represents thewaveform of the voltage developed in the secondary winding 47 of the apparatus of Figure l, while the curve 71 is representative of the voltageof the secondary winding 54. It`will be seen that, with respect :to the oscillator output wave 69, the wave 70 has a` lagging phase of approximately 60 or k3er/3 fradians. Also, by reason of the described 120" phaserelation'sl'iip',` between the kvoltages developed in the secondary `windings 47 an'd 54, the wave 71 Vis lagging the wave 70 by substantially 120 or 21r/ 3 radians. Preferably, the resistivecapacitive networks 49-51 and 554-56 of Figure 1 function to establish a clipping level indicated by the line 72 of Figure 2, so that only the crests of the waves 70 and 71'far'e effective to operatively condition the rectifier networks 48 and 57.

The curve 73 is generally illustrative of the form of the received composite color videol signal wave and for purposes of illustration, there have been indicated the'red, green and'A blue video signal components 74, 75 and 76 respectively `which constitute the image information contained in the received carrier wave. The color video signals, it will be noted, are spaced in time relative to one another by substantially 21r/ 3 radians, las indicated. In,`

Figure 2, there also are indicated the selected video signal components by means yof which the two-color image is to be reproduced from a-received three-color video signal. In the illustrative embodiment of the invention the re'- produced two-colorimageconsists of the colors orange and cyan which are'represented respectively by video Y signals 77 and 7S. vIt will be noted that ythe orange video signals 77 are selectedin coincidence with the crests of the wave 70 which lags thewave 69 by vr/3 radiansk and,

therefore occurs midway between the reception of the red and green video signal'components 74'and 75. Similarly,k the cyan video signal components 78 are selected under the" control of the wave 71 the crests of which lagv the crests of the wave 70v by 21r/ 3 radians. Accordingly, the cyan video signal 78 is selected midway between the reception of the green and blue video signals and 76 respectively.

kIn ordertoreproduce a completely accurate image from three-color receivedvideo signals, it is necessary thatthe received composite color videoy signal wave be sampled substantially in coincidence with the. reception of the three-color component video signals. If sampled at any other time, the received composite color video signal wave represents a combination of two of the component colors in varying degrees of intensity. However, in' accordance with the present invention, it is desired to'sample the received composite color video signalV wave at predetermined intervals intermediate of the pure color video signals in order to derive therefroma video signal having an intensity which is representative of a preselected lcom-l bination of two of the componentcolors.V yIt has`v been determined that ay two-,color image may be reproduced from a three-color video signal by timing the receiving sampling for occurrence substantially midway between the reception of the two selected primary color representative video signals. For example, in order to derive a signal representative of the orange color component of the image to be reproduced, the received composite color video sig- 'nal wave 73 is sampled at a point substantially midway between the red and green video'signals l74 and 75, respectively, to thereby develop an orange video signal component 77.` Sirnilarly,tl1ecyan video signal component V78 ofthe image to b'e reproduced is derivedlby timing the samplingoperationtov occur substantially midway between thegreen andblue video signals 75 and 76i Consequently, when the rectier bridge network 48 is rendered conducting under the control of the phase shifting` tube 26 at a` time which is substantially midway between the occurrence of the red and green video signals 74 and 75 of Figure 2, there is impressed upon the orange video signal amplifier 15 for subsequent control of the orange image kinescope 17 a video signal 77, the character of` whichis a combination ofthe red and green video signals and, therefore, is representative of the orange color component of the image to be reproduced. Similarly, the rectifier bridge network 57 is rendered conducting under the control of the voltage developed in the secondary` winding-54 as a result of theoperation of the phase shifting tube 27 at the time when the received composite color video signal wave 73 is substantially midway between the green and blue video signals 75 and 76 so that a cyan video signal-78 is impressed upon the cyan video signal 16 for ultimatek control of the cyan reproducing kinescope 18. v

It is to be understood that the invention is not necessarily limited to the details of the illustrative embodiment described, wherein the apparatus has been assumed to be adjusted in such a manner as to combine the green and red received video signals in suitable proportions to produce signals representative of the orange color component of the image, and the blue and green video signals are combined suitably to develop signals representative of the cyan color component of the image. It, also, is within the scope of the present invention to adjust the capacitors 31, 39 and 44 so as to select, from the received threecolor video signal wave, properly timed voltage samples representative of a combination of the red and blue video signals. thegreen and red or the blue and green color combinations; It is seen that the particular color video signals, which are to be mixed for the development of a signal representative of a combination of any pair of the primary color components of the image, are selected by suitably adjusting the phase shifting device 25 so that the two `voltages developed in the secondary windings 47 and 54-are properly phased with respect to the received threecolor video signal wave to etlect the operation of the keying devices 13 and 14 at the desired intervals occurring between the reception of the selected pairs of primary color vdeo signals.

It also will be understood that the present invention is not limited for use with apparatus for reproducing a twocolor image from three-color video signals. trary, the principles disclosed in the illustrative embodiment of the invention may be employed with substantially equal facility for the reproduction of a color television image in any number of colors smaller than the number of colors represented by the received video signals. For example, either a two-color or a three-color image may be reproduced from received four-color video signals.

It also will be appreciated that the present invention has the advantage of providing a means for producing a relatively simple and inexpensive adaptor for the purpose of converting a monochrome receiver for the reproduction of a colored image. Such an adaptor embodying the invention requires a minimum number of additional apparatus components. For example, a monochrome receiver may be adapted to reproduce a two-color television image from video signals representing three or more color components by the addition of only one image reproducing device, together with the timing apparatus in accordance with .the present invention for suitably energizing the two image reproducing devices.

There has also be proposed an arrangement for producing dot interlace in order to improve image reproduction. Methods and apparatus for producing dot interlace have been well shown and` described'in the copending` U. S: applicationsto Randall Ballardl entitled Colon Such a combination may be used instead of either On the con- Television Systems?" SN- 117,528; filed September 24, 1949, and-Alfred. C.` Schroeder entitled Color Television," SN 117,593, led September 24, 1949. It will be understood that'the present invention is applicable for the reproductionof images in color in conjunction with arrangements of thev type suggested in the above identified application;

Accordingly, it is intended that the foregoing disclosure of an` illustrative embodiment of the invention be considered as teaching the principles underlying the invention, the scope of which may be determined from the following claims.

1. In a multi-color television system wherein each elementalimage area is representedl by color signals producing a modulated envelope of a carrier wave, apparatus for reproducing said'image in a smaller number of colors than are represented by said color signals, comprising an image reproducing device for each of the colors in which the image is to be reproduced, means for demodulating said carrier wave, and electronic'switching means coupled between said demodulating` means and said image reproducing devices for impressing momentarily said dcmodulated wave successively upon said image reproducing devices at predetermined intervals following the reception of predetermined ones of said color signals.

2. In a multi-colorV television system wherein each elemental image area is represented by successive groups of a plurality of time-spacedV color signals producing an amplitude-modulated envelope of a carrier wave, apparatus for reproducing said image in a smaller number of colors than are represented by said color signals, comprising an image reproducing device for each of the colors in which the image is to be reproduced, means for demodulating said carrier wave, and electronic switching means coupled between said demodulating means and said image reproducing devices for impressing momentarily said' demodulated wave successively upon said image reproducing devices at predetermined intervals between the occurrence of selected different pairs of said color signals, one pair of said color signals being selected for each color in which the image is t0 be reproduced.

3. ln a multi-color television system wherein each elemental image area is represented by successive groups of a plurality of time-spaced primary color signals producing an amplitude-modulated envelope of a carrier wave, apparatus for reproducing said image in a smaller number of colors than are represented by said primary color signals, comprising` means for receiving and demodulating said carrier wave, an image reproducing device for each of the colors in which the image is to be reproduced, means operative for short periods at predetermined times following the reception of predetermined ones ofvsaid primary color signals for selecting, from said demodulated wave, mixed color signal voltages, one of said'mixed signal voltages being selected for each of the colors-in which the-image is to be reproduced, and means for impressing said selected mixed signal voltages respectively upon said image reproducing devices.

4; In` a multi-color-V television system wherein each elemental imageI area is represented by color signals producing an amplitude-modulated envelope of a carrier wave; apparatusfor reproducing said image'in a smaller number of colors than are represented by said color signals, comprising means for receiving and demodulating said `carrier wave, an image reproducing device for each of the colors in which the image is to be reproduced, electronic switching. means for selecting, from said demodulated wave, mixed signal voltages intermediate of different pairs of said plurality of color signal voltages,

none of' said mixed signal voltages being selected for each of` the'colors in which the image is to be reproduced, and means for impressing said selected mixed signal voltages respectively upon said image reproducing devices.

5.' ln a multi-color television system wherein each `elemental image amavis-represented by successive groups of `a plurality of time-spaced primary color signals 'producing an amplitude-modulated envelope of a carrier wave, apparatus for reproducing said image in a smaller number of colors than are represented by said color signals, comprising means for receiving and demodulating said carrier wave, an image reproducing device for each of` the colors in which the image is to be reproduced, a

source of timing impulses controlled by and operating in' elemental image area is represented by three color signals producing a modulated envelope of a carrier wave, apparatus for reproducing said image in two colors, each being a predetermined combination of two dilerent pairs of :said three colors, comprising means for receiving and demodulating said carrier wave, Vtwo image reproducing devices for displaying respectively said two predetermined color combinations, and electronic switching means coupled to said receiving anddemodulatingmeans and to said'image reproducingdevices for momentarily impressing said demodulated wave alternately upon said image :reproducing devices at predetermined intervals after. 'the occurrence of Itwo different ones of- 'said three color signals.

y7. Inv -aV three-color television system wherein each elementalimage area is represented by three color signals producing an amplitude-modulated envelope of a carrier wave,'apparatus for reproducing said image in two colors,

each being a predetermined combination of two diiierent pairs of saidrthree colors, compri-sing means for receiving and demodulating said carrier wave, two image reprodu'cingidevices for displayingrespectiv'ely said twoy prev determined color combinations, and electronic switching means-coupled to said receiving and demodulating means and Vtoisaid image reproducing devices for impressing said demodulated wave alternately upon said image reproducing devices at predetermined intervals substantially midway between the occurrence of'two different pairs of said three colorsignals.` t 2 v 8. In a three-color television systeml wherein each elemental image area isrepresented by three color signals producing anl amplitude-modulated envelope of a'carrier wave, apparatus for reproducing said image in'two colors, each `beinga predetermined combination of twodierent pairs of v,said three colors, comprising means 'for receiving and demodulating said` carrier wave, twoimage reproducing devices for displaying respectively said two selected color combinations, and electronic switchingmeans coupled to said receiving and demodulating means and to said image'reproducing devices" for impressing said demodulated wave alternately upon saidirnage reproducing devices at predetermined intervalsbetween the 'occurrence of two differennpairs of said three color sign-als.'

9.A In a three-color television systeml wherein each elemental image area is represented by three color signals producing'an amplitude-modulated.envelope of a carrier wave, apparatus for reproducingk said image in two colors, ea'ch beinga predetermined combination of two diiere'nt pairs of'said three colors, comprising means for receiving -and demodulating said carrier wave, two image reproducing devices for displaying respectively said two selected color combinations, electronic switching means for selecting, from' said demodulated wave, portions intermediate of eachoftwo different pairs vofvsaid three color signals, said selected wave -portions'fbeing 'representativeA of. said ypredetei'minedcolor combinations,' and means for impressing said selected wave portions respectively upon said two image reproducing devices.

l0. Apparatus for reproducing a two-color image from three-color signals, said signals constitutinga wave having a varying amplitude representative of the three-color content of each of a succession of elemental image areas, said apparatus comprising a kinescope for each of the two colors in which the image is to be reproduced, a gating device having an input and an output for each of said kinescopes, said gating devices being normally inoperative to transfer signals from said inputs to said associated outputs and adapted to be operated periodically to transfer signals from said inputs to said associated outputs, means for eiectively coupling said outputs respectively to said kinescopes to control the operation of said respective kinescopes, means for impressing said threecolor signals simultaneously upon the inputs of both of said gating devices, and means for alternately operating said gating devices at predetermined intervals between selected pairs of said three-color signals.

1l. In a two-color television system, means for'receiving a carrier wave having a signal-modulated envelope varying in amplitude in accordance with the three primary color content of successive elemental image areas, a source of timing impulses having a frequency corresponding to the frequency of any one of said color signals, a rst image reproducing device fordisplaying a first combination of two of said primary colors, a second image reproducing device for displaying a second and diierent combination of two of said primary colors, two normally inoperative keying devices coupled respectively to said image reproducing devices and to said receiving means and respectively operative at different times to render the associated yimage reproducing devices responsive to selected portions of said modulation envelope, and a phase shifting device coupled to lsaid timing impulse source and to said respective keying-devices to condition '.said keying devices for individual operation at predeterminedl intervals occurring between the reception of two different pairs of said color signals. y

l2.l In a two-color television system, means for receiving a carrier wave having an amplitude-modulated envelope produced by recurring series of time-spaced signals respectively representative of three primary colors of successive elemental image areas, means coupled to said receiving means for developing a train of timing impulses having a frequency corresponding to the recurrence frequency of any one of said colorsignals, a rst image reproducing device for displaying ay lirst combination of two of said primary colors, a secondimage reproducing device for displaying a second and diierent combination of two of said primary colors, two normally inoperative keying devices coupled respectively to said image reproducing devices and to said receiving means and individually operative-to render the associated image reproducing devices responsive to selected portions of `said modulation envelope, and a phase shifting device coupled between said timing impulse developing means and said respective keying devices to condition said keying devices for alternate operation at predetermined intervals occurring between the reception of two different pairs of said color signals.

13. In a three-color television system wherein each elemental'image area is represented by three 120 outof-phase color signals producing an amplitude-modulated envelope of a carrier wave, apparatus for reproducing said image in two colors, each being a predetermined combination of two different pairs of said three colors, comprising means for receiving and demodulating said carrier wave, two image reproducing devices for displaying said two predetermined color combinations, electronic switching means operating to momentarily impress said demodulated waves alternately upon said image reproducing devices, and'means operating synchronously with said received signals for operatively controlling said lswitching means at predetermined intervals substantially 11 60 out-of-phase with 'two different ones of said color signals.

14. In a color television system, signal producing apparatus comprising in combination, means receiving a composite video signal wave the amplitudes of which at predetermined phases represent respectively a plurality of component colors of a subject, video signal-deriving apparatus responsive to said composite wave and operable by control waves of suitable phases to derive individual video signals from said composite wave representative of subject colors indicated by said control wave phases, and means to impress polyphase control Waves upon said video signal-deriving apparatus for operating said apparatus in phases at least one of which is different from said predetermined phases, whereby said produced individual video signals respectively represent a plurality of colors at least one of which differs from said subject component colors.

15. In a color television system, signal producing apparatus comprising in combination, means receiving a composite video signal wave the amplitudes of which at predetermined phases represent respectively a plurality of component colors of a subject, video signal-deriving apparatus coupled to said receiving means and operable in response to control waves of suitable phases and to said composite video signal wave to derive individual video signals from said composite wave, and means coupled to and impressing control waves of different phases upon said video signal-deriving apparatus for operating said apparatus in phases other than said predetermined phases, whereby said produced individual video signals respectively represent a plurality of colors differing from said subject component colors.

16. In a color television system, signal producing apparatus comprising in combination, means receiving a composite video signal wave having a predetermined color repetition frequency -and the amplitudes of which at predetermined phases represent respectively a plurality of component colors of a subject, apparatus coupled to said receiving means and operable in response to a control wave and to said composite video signal wave to derive individual video signals from said composite wave, a source of a control wave having said predetermined frequency, and means impressing said control wave upon said apparatus in phases, other than said predetermined phases, whereby said derived individual video signals respectively represent a plurality of colors differing from said subject component colors.

17. In a multi-color television system wherein a composite video signal wave of predetermined frequency has instantaneous amplitudes representative respectively of the color components of successive elemental areas of an image to be reproduced, composite video signal wave receiving apparatus comprising, video signal-deriving means operable to produce individual video signals representative respectively of the colors in which said image is to be reproduced, means impressing said composite video signal wave upon said signal-deriving means, a source of a reference wave having said predetermined frequency, means coupled to said reference wave source to develop a different phase of said reference wave for each of the colors in which said image is to be reproduced, and means impressing respective phases of said reference wave upon said signal-deriving means to produce said individual color-representative video signals, the particular colors represented by said individual video signals being dependent upon the phase relationship of said individual reference wave phases and said composite video signal wave, said reference wave phases having a relationship to said composite video signal wave differing from that of said instantaneous video signal wave amplitudes.

18. In a multi-color television system wherein a signal wave of predetermined frequency has amplitude and phase variations representative respectively of the saturation and hue of successive elemental areas of a color image to be reproduced, predetermined phases of said signal wave representing predetermined component colors of said image, signal wave receiving apparatus comprising means for obtaining said signal wave of predetermined frequency, colorrepresentative video signal-deriving means, a source of a reference wave having said predetermined frequency, means coupled to said reference wave source to develop a dierent phase of said reference wave for each of the colors in which said image is to be reproduced, and means impressing respective phases of said reference wave and the obtained signal wave upon said signal-deriving means to produce individual color-representative video signals, the particular colors represented by said individual video signals being dependent upon the phase relationship of said individual reference wave phases and said obtained signal wave, said reference wave phases having a relationship to said video signal wave differing from said predetermined phases.

19. Color television receiving apparatus for reconstituting an image signal in color controlled by reception of a signal wave of a selected frequency having imposed thereon phase and amplitude changes which are representative respectively of the hue and saturation of successive elemental areas of a scanned image to be reproduced by said receiving apparatus, predetermined phases of said signal wave representing respectively predetermined component colors of said image; said receiving apparatus comprising means operable to obtain said signal wave, a reference wave source providing an unmodulated wave of said selected frequency, a plurality of separately adjustable means coupled to said reference wave source, each of said last named means being operable to develop a different phase of said reference wave, one phase for each of the selectable component colors in which the reproduced image is to be rendered, a plurality of signal sampling means, means for impressing the obtained signal wave and the respective phases of said reference wave each upon one of said sampling means to produce a plurality of individual color-representative video signals, the particular colors represented by said individual video signals being dependent upon the compared phase relationship of said individual reference wave phases and said obtained signal wave, said reference wave phases having a relationship to said obtained signal wave differing from said predetermined phases.

20. In a color television receiver for reproducing a twocolor image from a video signal wave of a given frequency and having phase variations effectively indicative of the colors of an object, video signal producing apparatus including in combination: video signal-sampling means responsive to said video signal wave and operable by control waves of suitable phases relative to a predetermined phase of said video si'gnal wave to derive individual color-indicative video signals from said video signal wave; and means to impresstwo control waves of said given frequency and having different phases relative to said predetermined phase of said video signal wave upon said sampling means to produce two video signals respectively indicative of the two colors in which said image is to be reproduced.

21. In a color television receiver for reproducing a twocolor image from a video signal wave of a given frequency and having phase variations effectively indicative of the three-color content of an object, video signal producing apparatus including in combination: video signal-sampling means responsive to said video signal wave and operable by control waves of suitable phases relative to a predetermined phase of said video signal wave to derive individual color-indicative video signals from said video signal wave; and means to impress two control waves of said given frequency and having different phases relative to said predetermined phase of said video signal wave upon said sampling means to produce two video signals respectively indicative of two different colors of said object, said two different object colors being determined by the phase relationship of said control waves to a predetermined phase of said video signal wave.

22. In a color television receiver for reproducing a twocolor image from a video signal wave of a given frequency and having amplitude and phase variations effectively indicative of the three-color content of an object, video signal producing apparatus including in combination: video signal-sampling means responsive to said video signal wave and operable by control waves of suitable phases relative to a predetermined phase of said video signal Wave to derive individual color-indicative video signals from said video signal wave; and means to impress two constant amplitude control waves of said given frequency and of different phases relative to said predetermined phase of said video signal wave upon said sampling means to produce two video signals respectively indicative of two different colors of said object, said two different object colors being determined by the phase relationship of said control waves to said predetermined phase of said signal wave.

23. In a color television receiver adapted to receive a video signal wave having a given frequency, certain phases relative to a predetermined phase of said wave effectively indicating certain colors of an object, video signal producing apparatus including in combination: video signalsampling means responsive to said received video signal wave and operable by control waves in suitable phases relative to said predetermined phase vof said video signal wave to produce video signals respectively indicative of other object colors dilering from said certain object colors; a source of control waves having said given frequency and having respective phases differing from said certain video signal wave phases and corresponding respectively to phases relative to said predetermined phase of said video signal wave which elfectively indicate said other object colors; and means for impressing said control waves upon said sampling means to produce said video signals.

24. In a color television receiver adapted to receive a video signal wave having a given frequency, two phases relative to a predetermined phase of said wave effectively indicating two selected colors of an object, video signal producing apparatus including in combination: video signal-sampling means responsive to said received video signal wave and operable by control waves in suitable phases relative to said predetermined phase of said video signal wave to produce video signals respectively indicative of two object colors diierent from said two selected object colors; a source of two control waves having said given frequency and having respective phases differing from said two video signal Wave phases and correspond- `ing respectively to the two phases relative to said predetermined phase of said video signal wave which effectively indicate said two different object colors; and means for impressing said two control waves upon said sampling means to produce said video signals.

25. In a color television receiver adapted to receive a video signal wave having a given frequency, certain phases relative to a predetermined phase of said wave effectively indicating certain colors of an object, video signal producing apparatus including in combination: video signal-sampling means operable by control waves in suitable phases relative to said predetermined phase of said video signal wave to produce video signals respectively indicative of other object colors differing from said certain object colors; means for impressing said received video signal wave upon said sampling means; a source of a wave having said given frequency; means coupled to said wave source to develop two control waves having respective phases differing from said certain video signal wave phases and corresponding respectively to phases relative to said predetermined phase of said video signal wave which effectively indicate said other object colors; and means for impressing said control waves upon said sampling means to produce said video signals respectively indicative of said other object colors.

26. In a color television receiver adapted to receive a video signal wave having a given frequency, a given number of certain phases relative to a predetermined phase of said wave effectively indicating said given number of component colors of an object, video signal producing apparatus including in combination: video signalsampling means responsive to said received video signal wave and operable by control waves in such given phase relationship to said predetermined phase of said video signal wave as to produce video signals effectively indicative of a number of component colors of said object smaller-*than said given number; a source of control wave energy having said given phase relationship to said predetermined phase of said video signal wave; and means for impressing said control wave energy upon said sampling means to produce said video signals.

References Cited in the file of this patent UNITED STATES PATENTS 

